Modern global cellular and non-cellular positioning technologies are based on generating large global databases containing information on cellular and non-cellular signals. Such databases are also referred to as radiomap databases. The information may originate entirely or partially from users of these positioning technologies. This approach is also referred to as “crowd-sourcing”.
The information provided by users is typically in the form of “fingerprints”, which contain a location that is estimated based on, e.g., received satellite signals of a global navigation satellite system (GNSS) and measurements taken from one or more radio interfaces for signals of a cellular and/or non-cellular terrestrial system. In the case of measurements on cellular signals, the results of the measurements may contain a global and/or local identification of the cellular network cells observed, their signal strengths and/or pathlosses and/or timing measurements like timing advance (TA) or round-trip time. For measurements on wireless local area network (WLAN) signals, as an example of signals of a non-cellular system, the results of the measurements may contain a basic service set identification (BSSTD), like the medium access control (MAC) address of observed access points (APs), the service set identifier (SSID) of the access points, and the signal strength of received signals (received signal strength indication RSSI or physical Rx level in dBm with a reference value of 1 mW, etc.).
This data may then be transferred to a server or cloud, where the data may be collected and where further models may be generated based on the data for positioning purposes. Such further models can be coverage area estimates, communication node positions and/or radio channel models and/or Rx fields, with base stations of cellular communication networks and access points of WLANs being example communication nodes. In the end, these refined models may be used for estimating the position of mobile terminals. The generated models may be stored in a radiomap database, optionally together with the collected data.
A positioning of a mobile terminal that is to make use of the radiomap can function in two modes. The first mode is a terminal-assisted mode, in which the terminal performs measurements on a cellular and/or non-cellular air interface and provides the measurement results to a remote server. The server carries out positioning computations for the terminal based on the received measurement results and the information in the radiomap database, and provides a position estimate back to the terminal. The second mode is a terminal-based mode, in which the terminal has a local copy of the radiomap or a subset of the global radiomap. Such a subset can be downloaded by the device from a remote server for the area of interest, for instance a small area around the current location, for a whole country, or some other region. The subset can also be pre-installed to the terminal in the factory. Also in this case, it may be desired to update the data at some point.
It may be noted that even when using a mobile terminal having GNSS-capabilities, a user may benefit from using cellular/non-cellular positioning technologies in terms of time-to-first-fix and power consumption. Also, not all applications require a GNSS based position. Furthermore, cellular/non-cellular positioning technologies work indoors as well, which is generally a challenging environment for GNSS based technologies.